A. Gocht

Blockade of Tyrosine Kinases as Preventive Strategy Against Cardiac Allograft Vasculopathy in a Murine Aortic Transplant Model

Objectives Previous reports suggest a role of platelet derived growth factor (PDGF) in the development of cardiac allograft vasculopathy (CAV). The pharmaceutical blockade of tyrosine kinases may alter the expression of different growth factor receptors: platelet derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) and hereby play a role in the context of cardiac allograft vasculopathy. Therefore the aim of this study was to determine the impact of tyrosine kinase inhibition on the development of cardiac allograft vasculopathy in a mouse model. Methods Fully allogeneic mouse aortas from C57BL/6 mice (H2b) were abdominally transplanted into CBA mice (H2k). Recipients were treated with tyrosine kinase inhibitor nintedanib (60mg/kg/d) and sacrificed on day 14 for cytokine PCR analysis of the graft or on day 30 for (immuno-) histological measurements. Results Aortic grafts treated with tyrosine kinase inhibitor nintedanib showed significantly reduced neointima proliferation (33% ± 12% vs. 54% ± 13%) after 30 days. These findings go along with significantly reduced amounts of smooth muscle cells (SMC) (20% ± 9% vs. 42% ± 10%) within the neointima. Further immunofluorescence analysis revealed no relevant difference in the percentages of dendritic cells, macrophages and CD4+ T-cells within the neointima. Meanwhile, the expression of both PDGF receptor subtypes &agr; and &bgr; was reduced within the neointima of the aortic grafts. Additionally, we found a reduced gene expression of the ligand PDGF-B, a mitogen for SMC, and of the pro-inflammatory CD40L. Conclusion PDGF receptor blockade via inhibition of receptor tyrosine kinases seems to be a promising way to prevent the development of cardiac allograft vasculopathy in a mouse model. We would speculate a direct inhibition of the migration and proliferation of smooth muscle cells with a resulting decrease of neointima formation as the mechanism of action.

Effects of different serotonin receptor subtype antagonists on the development of cardiac allograft vasculopathy in murine aortic allografts

BACKGROUND Cardiac allograft vasculopathy (CAV) is the main obstacle for long-term survival after heart transplantation. Alloimmune mediated chronic vascular rejection results in several mechanisms like platelet activation, immigration of inflammatory cells through the endothelial layer and proliferation and migration of smooth muscle cells (SMCs). Serotonin (5-HT) promotes these processes via activation of 5-HT2 receptors. We hypothesized that inhibiting 5-HT2 receptors ameliorates the development of CAV. METHODS CBA/JRj mice recieved aortic grafts from C57BL/6 mice. After transplantation until recovery of organs, recipients were treated with serotonin receptor antagonists: sarpogrelate (5-HT2A), SB 204741 (5-HT2B) or terguride (5-HT2A+B). Mice were sacrificed after 14 days for qRT-PCR analysis or after 30 days for histological evaluation. Serum serotonin ELISA was done at both time points. RESULTS Elevated serum serotonin levels were significantly reduced after 5-HT2A antagonist treatment as was 5-HT2A receptor expression. This went along with reduced inflammation characterized by significantly fewer infiltrating macrophages and pro-inflammatory intragraft cytokines and with reduced tissue remodeling evident as significantly less neointima formation. CONCLUSION Inhibition of the 5HT/5-HT2A receptor axis leads to significantly reduced neointima proliferation after aortic transplantation associated with reduced transendothelial migration of macrophages and decreased expression of inflammatory cytokines. These findings have translational implications as inhibitors of 5HT2A like sarpogrelate are already approved for clinical use.

New Targets for the Prevention of Chronic Rejection after Thoracic Organ Transplantation

Abstract The gold standard for the treatment of terminal heart failure and irreversible lung diseases includes thoracic organ transplantation. The major obstacle for long‐term survival after successful transplantation is chronic rejection, an ongoing immunomodulatory disease so far without effective therapy. Therefore, the aim of this review is to elucidate scientific efforts targeting different new mechanisms of cardiac allograft vasculopathy (CAV) and chronic lung allograft dysfunction (CLAD). For this purpose, we performed a systematic review of the literature to assess recent strategies in transplant immunology research. We searched MEDLINE from 2015 up to date for articles addressing the following keywords: CAV, transplant vasculopathy, transplant arteriosclerosis, CLAD, bronchiolitis obliterans transplant, and obliterative bronchiolitis transplant. All articles including experimental models in the field of transplant immunology addressing new aspects for the prevention of chronic rejection after heart and lung transplantation were included in this review. The prevention of chronic rejection would clearly improve the survival of patients after heart and lung transplantation. Interesting targets were addressed in recent research, but further research is necessary to effectively treat this life‐threatening disease in transplant recipients.